The goal of this project is to elucidate the molecular mechanisms underlying the propagation and receipt of biochemical signals by cells, with particular emphasis on the means by which certain hormone and neurotransmitter messages are communicated across the plasma membrane. This research direction has evolved during 6 years of studies in this Laboratory on cell surface component changes, in particular those components involved in the induction and mechanism of action of beta-adrenergic and cholera toxin receptors. These studies will continue with increased emphasis on the biochemical events involved in the maintenance of cell surface receptors and in the phenomenon of desensitization. As an extension of this work, the role of tropic hormones in central nervous system control of pituitary function will be examined in culture cells. As a specific example, the possibility of a role for phospholipid methylation in the response of the pituitary cell line GH3 to TRH by release of prolactin will be explored. Further studies on the mechanism of transmembrane signalling will exploit the properties of some recently derived hybrid cell lines which contain several different hormone/neurotransmitter receptors on a single cell.